Process for desulphurizing gases



Patented Mar. 8, 1938 J UNITED SII'ATES PATENT OFFICE a PROCESS FOR PESULPHURIZING GASES Otto Roelen Mnlheim-Ruhr, and Walter Feisst, Oberhausn-Holten, Germany, assignors to Studienund Verwertungsgesellschait mit beschrlnkter Hai'tung, Mulheim-Buhr, Germany No Drawing. Application January 23, 1935, Serial No. 3,094. In Germany January 31, 1934 4 Claims. (01. 23-3) Our invention relates to the purification of gases and more especially to the removal of sulphur compounds from gas mixtures and quite particularly from mixtures containing carbon hate and iron oxide. This mixture may then be used in the form of powder or in the form of briquettes made from the powder. It is, however, advantageous to bake the mixture that has 5 monoxide and hydrogen. been stirred with water to produce a stifl paste, 5

It is known that organic sulphur compounds by the application of heat, until a solid mass is can be removed from gases containing carbon produced; this is broken up into hard lumps, monoxide and hydrogen by passing the gases over which retain their shape or mechanical comcarbonates of the alkaline metals at a high tempactness even at the reaction temperature, and

perature. As the purifying capacity of the subnotwithstanding this, they can be used eflec- 10 stances mentioned, however, remains confined tively for the P y g operation by reason .of practically to the removal of organic sulphur the great porosity of the whole mass. The shap: compounds these substances are of no use for ing and loosening of the mass can be assisted by purifying sulphur commercially. the use of binders such as waterglass or by other It has been found that it is possible for the additions such as kieselguhr. 1

sulphur to be completely removed without there The object of the process according to the being left any trace of newly formed hydrogen invention is to desulphurize those gases which sulphide in the gas that is being removed, that contain carbon monoxide in addition to hydrois to say, by treating the gases at temperatures gen. It is known, however, that iron or iron comof not higher than 300 with alkali carbonates pounds, particularly when in the presence of 20 which have been intimately mixed with reactive alkali, give rise to a catalytic effect in various oxides or hydroxides of iron and constitutes as ways with mixtures of carbon monoxide and high a part as approximately 10% or more of this hydrogen when at high temperatures. It has mixture. It has been found that purifying combeen found that notwithstanding this fact, it is P unds which consist of such mixtures are capossible according to the present invention com- 5 pable of removing all the sulphur compounds pletely to desulphurize those gases which contain very effectively, so that if the work be carried carbon o d in addition to yd Without properly there is no trace left of sulphur, out undesirable subordinate reactions of the careither in organic combination or as hydrogen sulbon monoxide occurring in the completely desulphide. This reaction was neither known nor phurized gas. The mixtures of alkali carbonate 30 could it have been anticipated. Gas purifying and iron oxide produced by the method hereincompounds known as alkalized compounds before described, exert a complete desulphurizing which contain only a small percentage of alkali action even at considerably lower temperatures and are intended merely for producing an alkathan those at which, as experience has shown,

line reaction or for activating the hydrogen sulthe carbon monoxide is catalytically'attacked in 35 phide absorbed, do not take part in this reaction. the same compounds. Accordingly in carrying Such a reaction is dependent upon the presence out the purifying operation according to the presof large quantities of alkali carbonates amountent invention the r ion mpe atures are ing to at least approximately 10%, calculated on maintained so low that complete desulphuriza- 40 the mixture of alkali metal carbonate and retion is obtained, and'undesirable subordinate re- 40 active oxide or hydroxide of iron. Alkali caractions do not occur. bonate cannot be replaced by carbonates of alka- According to a known process the desulphuriline earths such as lime, as is the case, for exzation of gases is efiected by the use of alkaline sample, when producing "alkalized gas purifying substances or alternatively by the use of oxides compounds. and hydroxides of iron and zinc. Temperatures 5 It has been found that intimate mixtures of up to 500 C. however must be employed. When 1 to 2 parts or soda with 2' to 3 parts of reactive using the last mentioned substances with high oxides or hydroxides of iron are very effective. temperatures destructive subordinate reactions For this purpose suitable iron ores such as bog occur when gases containing carbon monoxide iron ore, as also the residues from the treatare used, whereby the composition of the purify- 50 ment of bauxite, which are generally used as ing gas immediately changes. When using the "dry gas purifying compounds may, for expurifying compounds according to the invention, ample, be used. For producing the mixtures dewhich likewise contain iron oxides and which in scribed it sufllces to rub together very intimately the use of considerably lower temperatures effect in a dry state the two constituents alkali carbothe complete removal of all the sulphur com- 55 pounds, in which it diflers from the known processes, these otherwise objectionable subordinate reactions or the gas constituents do not occur, so that during desulphurization the composition of the gas treated is not materially changed, that is to say, remains practically unaltered.

With a view to the avoidance oi undesirable subordinate reactions desulphurization may be continued at a relatively low temperature for example at between 200 and 230 until the composition is exhausted. Satisfactory purification is possible, however, by the use of substantially lower temperatures such as a temperature of about 100. A considerable increase in the. ei'ilciency of the purifying composition can be obtained however by gradually raising the reaction temperature in the composition up to a maximum of 300, in the way in which the activity of the mass with reference to the stopping of undesirable subordinate reactions decreases as the proportion of sulphur increases. If on the other hand the desulphurization be carried out under such conditions for example in apparatus suitable for the purpose, that increases in temperature are not possible in the purifying mixture,

higher temperatures than 230 may be employed from the outset without any objectionable subordinate reactions.

If the purifying compositions after being used for a correspondingly long period no longer pro duce a desulphurizing action at the higher temperature, their capacity for absorbing sulphur is not completely exhausted. It has been found that exhausted purifying mixtures after being moistened with water can be still further used for the purpose of removing hydrogen sulphide from the raw gases in known manner at room temperature.

Example Water gas containing no hydrogen sulphide, but about 30 grammes of organically combined sulphur per 100 cubic metres is conveyed at 230 at a velocity of 500 volumes of gas per hour through a reaction chamber over a purifying composition in small lumps, the composition being produced by the baking and breaking up or 1 part of soda and 2 parts oi! hydrated iron oxide (Luxmasse) or instead or the latter 2 parts of red slurry (Rotschlamm). Under these conditions 1 kg. of the mixture purifies 100 cubic metres of gas so thoroughly that there is no indication when the gas is tested by any of the usual methods that any sulphur remains in any form in the gas, and without the composition of the water-gas being changed.

If the reaction temperature is raised to 300 1 kg. of the composition purifies as much as 350 cubic metres of gas.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

We claim:

1. The process or desulphurizing gases containing C and H, which comprises passing such gases at a temperature ranging between 100 C. and 300 C. in contact with an intimate mixture of a reactive oxide of iron and an alkali metal carbonate, the alkali metal carbonate constituting approximately of the mixture.

2. The process of desulphurizing gases containing CO and H which comprises passing such gases at a temperature ranging between about 100 C. and 300 C. in contact with an intimate mixture containing a reactive oxide of iron and an alkali metal carbonate in the proportion of about 25 to 50% alkali metal carbonate to '75 to 50% oxide of iron.

3. The process of desulphurizing gases containing CO and H, which comprises passing such gases in contact with a mass consisting of a mixture of 1 to 2 parts of alkali metal carbonate with 2 to 3 parts of reactive oxide of iron, and gradually raising the temperature during operation of the process from about 100 C. to about 300 C.

4. The process of desulphurizing gases containing C0 and H, which comprises passing such gases in contact with a mass consisting of a mixture of 1 to 2 parts of alkali metal carbonate with 2 to 3 parts of reactive oxide of iron, and. gradually raising the temperature during operation or the process from about 230 C. to about 300 C.

O'I'I'O ROELEN. WALTER FEISST. 

